South Beach Steak

So, I hear the Steak Diane recipe is awesome, but I've yet to try it. Why bother, when there's one that already blows my socks off? It was the first dish I remember making when I first moved into my own apartment. I had my dad and stepmother over, and while they're the big champions of the Steak Diane, they wanted the recipe for this one too.
For a certain sweetie's birthday dinner tonight, I'm dusting it off once again. He knew he wanted something steaky, my stepmom's awesome sweet potatoes, and something green; the rest he left to me. I guess that means he must like my cooking!

Pan Roasted Steak and Onions
1 tbsp extra virgin olive oil
2 tbsp balsamic vinegar (use good stuff, trust me)
1 tbsp Worcestershire
1 tbsp Dijon mustard
2(ish) cloves of garlic
1 lb flank steak
1 tbsp fresh ground black pepper if you can swing it
1/2 tsp salt
1 c chook broth (I was the ff low sodium stuff)
1 medium onion, cut into rings, about 1/4 inch thick

In a large non reactive baking dish (no aluminum! I use Pyrex), combine the oil, vinegar, Worsh, mustard and garlic. Add the steak, turn to coat; cover and refrigerate for at least half an hour, turning once. You can make this the day before and refrigerate overnight too.
Coat a nonstick skillet with ff cooking spray and put over medium-high. Sprinkle the steak with s&p. Brown for 2 minutes per side. Add 1/2 c of the broth and cook, turning once for 5-6 minutes per side for medium rare (and why would you want it any other way?). Remove from skillet and cover loosely to keep warm. Reduce the heat to medium, add onion and cook til golden brown, about 4-5 minutes per side. Add the remaining broth as needed to prevent them from sticking.
Thinly slice the steak across the grain and serve smothered in the yummy onions.

Fantastic and not even unhealthy! You and your hips can thank me later. Your cholesterol might have to speak to my lawyers though.